1. Field of the Invention
The present invention relates to a color image forming apparatus. The present invention relates to a color image forming apparatus of electrophotographic type, electrostatic printing type, or the like, an information processing apparatus, and a control method thereof and, more particularly, to an image formation adjusting technique in a color image forming apparatus.
2. Description of the Related Art
A color image forming apparatus such as that shown in FIG. 23 has conventionally been utilized. This color image forming apparatus adopts, as a developing means, a rotary developing device 3 having a magenta toner developing unit 3M, cyan toner developing unit 3C, yellow toner developing unit 3Y, and black toner developing unit 3K. The rotary developing device 3 is rotatably supported by a rotation support (not shown). The respective color toner developing units sequentially face a photosensitive drum 4 to develop an image with each color toner.
In this arrangement of the developing means, the photosensitive drum 4 is driven to rotate at a predetermined angular velocity, and its surface is uniformly charged by a charger 8. An electrostatic latent image of the first color (e.g., magenta) is formed on the photosensitive drum by scanning a laser beam ON/OFF-controlled in accordance with image data of the first color. The magenta toner developing unit 3M for the first color develops and visualizes the electrostatic latent image. The visualized first toner image is transferred onto an intermediate transfer member 5 driven to rotate in press contact with the photosensitive drum 4 at a predetermined press force. This process is repeated similarly for the second to fourth color toners (cyan, yellow, and black toners). Toner images of the color toners contained in the respective developing units are sequentially transferred and superposed on the intermediate transfer member 5, forming a color image. For a full-color image, images of the four color toners are transferred onto the intermediate transfer member 5 and then transferred at once onto a printing material 6 fed from a paper feed unit. The printing material 6 is discharged outside after the fixing process by a fixing unit 7, obtaining a full-color print.
Recently, higher monochrome output speeds are demanded of even full-color image forming apparatuses in order to cope with office use and the like.
To satisfy the market demand, there has also been devised a color image forming apparatus with an arrangement shown in FIG. 24. A developing means in FIG. 24 incorporates a rotary developing device 3 and fixed black toner developing unit 3K. The rotary developing device 3 contains a magenta toner developing unit 3M, yellow toner developing unit 3Y, and cyan toner developing unit 3C. The rotary developing device 3 is rotatably supported by a rotation support. For a full-color output, the color toner developing units 3M, 3Y, 3C, and 3K sequentially face a photosensitive drum 4 serving as an image carrier to develop an image with each color toner. For a monochrome output, development is done using the fixed developing unit 3K without using the rotary developing device 3. With the arrangement in FIG. 24, even a full-color image forming apparatus can obtain the same monochrome output throughput as that of a monochrome image forming apparatus. Since the black toner is generally consumed in a large amount for office use and the like, the adoption of the fixed black toner developing unit described above can increase its capacity.
These days, demands have arisen for introducing the above-mentioned electrophotographic copying machine and full-color printer into the office or the like. In this situation, the rise time (warm-up time) impairs user friendliness. The rise time is the time until the color image forming apparatus can actually print out (the color image forming apparatus stands by) after the main body is turned on. The time which occupies a large proportion of the rise time after power-on is the time necessary for temperature adjustment of the fixing unit and image adjustment.
An electrophotographic color image forming apparatus has often used a method of finally thermally fixing, onto a printing sheet, toner transferred onto the printing sheet. Thus, temperature control of the fixing unit is important. Stable temperature adjustment control at high temperatures is requested because color development and fixing are achieved by sufficiently fusing toners and mixing colors.
When the color image forming apparatus is turned on while the fixing unit is at low temperature after, e.g., left to stand, the temperature of the fixing roller must be raised within a short time, and the entire fixing roller must be adjusted to a uniform temperature. To meet these requirements, there has been proposed a technique of using a fixing roller material with high thermal conductivity or making the surface layer of the fixing roller thin. Another approach is the use of toner which easily fuses uniformly even at low temperature.
Recently, density stability and tone stability of an output image are required along with an increase in full-color outputs. To achieve them, the following methods have been known as image control methods for color image forming apparatuses such as an electrophotographic copying machine and printer.
For example, after a color image forming apparatus is activated and its warm-up operation ends, a specific pattern is formed and its pattern density is read. The operation of a circuit such as a γ correction circuit which determines image forming conditions is changed on the basis of the read density value, thereby stabilizing the quality of a formed image.
According to another method, a specific pattern is formed and read again even when the tone characteristic changes upon variations in environmental conditions. The read density value is fed back to a circuit such as a γ correction circuit which determines image forming conditions, thereby stabilizing the image quality against the variation of the environmental conditions.
After long-term use of a color image forming apparatus, the read density of a pattern on an image carrier may become different from the density of an actually printout image. To solve this, there is also known a method of forming a specific pattern on a printing material and correcting image forming conditions in accordance with the density value.
According to still another method, a specific pattern is formed in a non-image area during the image forming operation to read the pattern density. The operation of a circuit such as a γ correction circuit which determines image forming conditions is changed every image forming operation, thereby correcting ever-changing image characteristics at high precision.
However, a further decrease in rise time until the standby state after power-on is an important factor in recent color image forming apparatuses.
Especially, a user who wants to output a monochrome image or a business document or the like, which does not put importance on tonality, immediately after power-on requires a color image forming apparatus with a short rise time till the standby state after power-on. As described above, the color image forming apparatus executes the temperature adjustment operation of the fixing unit after power-on and the image adjustment operation after the end of the warm-up operation. To shorten the rise time, there is proposed a method of executing these two operations at the same time. However, this method is unpreferable because it requires a large power amount and goes against recent trend toward energy saving.
Also, the following problems arise when a color image forming apparatus is used in the office where monochrome outputs occupy most of the outputs. That is, every time the color image forming apparatus is turned on, it must execute image control including density control and tone control to stabilize a full-color output image, though the output frequency of full-color images is low. The color image forming apparatus must execute full-color image control at intervals of a predetermined sheet count during monochrome output.
To solve these problems, the default image control settings and image control interval of a color image forming apparatus may be set in accordance with monochrome output. In this case, however, the full-color image control frequency is minimized, and the density and tone stabilities of full-color images cannot be assured for a user who frequently outputs full-color images. However, settings suited to full-color output decrease the throughput, and cannot satisfy a user who outputs many monochrome images. It is, therefore, difficult to make the default image control settings of all office-use color image forming apparatuses in different use environments.
Some of the above-described full-color image forming apparatuses employ a developing unit using a two-component developer containing a magnetic carrier and nonmagnetic carrier. In this case, for example, when low-density images are formed successively, degraded toner is discharged, or toner is applied into a band shape and used as a lubricant for the cleaner. However, in a full-color image forming apparatus used mainly for monochrome output, toner is consumed every time this control is executed, though color output is rare.
To solve this problem, a serviceman checks the use status of each user's full-color image forming apparatus, and designates an optimum control form matching the use environment of a user for each full-color image forming apparatus in accordance with the check result, optimizing each full-color image forming apparatus. For example, the serviceman checks the ratio of monochrome outputs and full-color outputs and the number of output sheets per predetermined period. Further, the serviceman adjusts, e.g., the density/tone correction control interval which starts as the down sequence during continuous output on the basis of use requirements from a user.
In this conventional practice, a serviceman must go to the location where each full-color image forming apparatus is installed, collect pieces of information, and set the full-color image forming apparatus.
To eliminate serviceman's trouble, there is proposed a system which allows a maintenance personnel at a remote place to obtain output sheet count information and use location environment information from a color image forming apparatus via a network, and to provide optimum parts and optimum setting values to a user on the basis of the obtained pieces of information (see, e.g., patent reference 1).
[Patent Reference 1] Japanese Patent Laid-Open No. 2004-101545
According to this arrangement, the serviceman grasps the environment of the use location of a color image forming apparatus and the number of output sheets by a user from a remote place using a network without visiting the user's office, and provides optimum parts and setting values. This can eliminate serviceman's trouble and greatly reduce labor costs. However, this arrangement cannot satisfy the above-mentioned purpose to optimize a color image forming apparatus in accordance with the use form of each user. In particular, this arrangement can achieve neither optimization of activation conditions corresponding to the use status such as the ratio of monochrome outputs and full-color outputs, nor an increase in throughput during continuous output. These demands arise from most users who use full-color image forming apparatuses in the office.
In addition, this arrangement requires the intervention of a maintenance personnel when providing optimum parts and setting values in accordance with obtained information. From this viewpoint, this arrangement is considered an extension of a conventional service which requires a serviceman to visit each user's office and optimize each full-color image forming apparatus.